Mantain's Trainer

An old man is a character of the day who appeared in Steamboat Willies!. This article will refer to him by his title, as he was unnamed in the episode.

He is the owner of the Wailord-shaped steamboat, which is known to take travelers to Hearthome City. When Ash and his friends decided to get supplies before leaving, the old man offered to watch their Pokémon on the ship, where Pikachu and the other Pokémon were left to their own devices. However, the old man quickly fell asleep and failed to watch them. The vessel left harbor after Pachirisu accidentally jump started the engine, and was headed directly towards a waterfall. The old man woke up in time and alerted Ash's group to the situation, even offering them his Mantine to help the Pokémon trapped on the boat before it goes over a waterfall.

The old man was apologetic for the mishap, though Ash and the others were glad the crisis was averted.

(Source: Bulbapedia)